Loud-speaker



April 1930. .c. A. (HOXIE 1,752,909

LOUD SPEAKER Filed Sept. 15, 1922 5 28 "Fig.1.

I Inventor:

Charles A.Hoacie His Attorney, I

Fatentecl Apr. 1,- 1930 NITED STATES PATENT, OFFICE CHARLES A. HOXIE, SCHENECTADY, NEW YORK, A SSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK LOUD-SPEAKER Application filed September 13, 1922. Serial No. 588,088.

My present invention relates to sound reproducing devices, and more particularly to devices capable of actuation by electric currents and adapted to reproduce faithfully and in good volume sounds by means of which the actuating currents have been produced.

One disadvantage which has been present in most devices which have been used for the purpose set forth above has been the fact that the necessary moving elements employed have possessed natural rates of vibration within the range of frequency of the sounds to be reproduced, and as a result sound having a frequency corresponding to this natural frequency have been accentuated more than sounds of other frequencies, and distortion has resulted.

One of the. objectsof my invention is to overcome this disadvantage and provide a device the moving elements of which have no natural rates of vibration within the range of the readily audible frequencies.

My improved device belongs-to the general class in which the sound producing diaphragm is actuated by means of a movable element which in turn is directly actuated by the electric currents applied to the device. If either the diaphragm or the actuating element therefor have natural rates of vibration within the range of frequency of the sounds to be reproduced, the distortion mentioned above will be present." I prevent such distortion by constructing both the diaphragm I and the actuating element therefor in such a 5 way that the will have no objectionable natural rates 0 vibration. The diaphragm actuating element which I employ is in the form of an elongated member supported at both ends and of such rigid construction that any natural rate of vibration which'it may have will be greater than the frequency of any of the sounds to be reproduced Another essential feature of such a device is that the moving parts shall have small consideration has consisted of a thin flexible sheet of metal or other material, such as mica, rigidly secured at its periphery. Such diaphragms usually have at least one, and in some cases more than one, natural rate of v1- bration within the range of frequency of the sounds to be reproduced. I overcome this disadvantage by employing a diaphragm of rigid construction and securing it in the device in such a way that the only movement of one part of the diaphragm with respect to another part takes place at or near the periphery. In other words, the greater portion of the diaphragm moves as a whole, and

substantially all of the internal stressesproduced take place near the periphery. This result may be conveniently brought about by making the diaphragm in the form of a cone having its base surrounded by a flat narrow ring by means of which it is secured in the device.

Thenovel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation will best be understood by reference to the following description taken in connection with the accompanying drawing, in which Fig. 1 is a vertical cross-section of one of my devices; Fig. 2 is a perspective view with a portion of the actuating mechanism removed,

and Fig. 3 is a perspective view of the actuating coils and the mounting therefor.

As indicated in the drawing, a base 1 is provided having attached thereto an upri ht support member 2. The actuating mec anism comprises a pair of permanent magnets 3 and 4, each of which has opposing poles 5, 5 separated by'a short air gap. .The magnets are held in proper spaced relation to 'each other by a bridging member 6, to which they ma be secured in any desired manner. The bri ging member 6 is secured bymeans of screws 7 to the bracket 8 which is formed on the member 9. The upright supporting member2 is provided with posts 10,v 10 and 11, 11. The diaphragm actuating member 12 is secured to the posts 10, 10 by means of the screws 13, '13 as indicated. The actuating member 12 is in the present case made of a tube of light metal, such as aluminum, sup

flattened at its middle portion. Before the tube is flattened a sleeve 14 of magnetic material is slipped on it and flattened with the tube to form an armature. The magnets 3 and 4 are so mounted that the armature 14 j is located in the air gaps of the magnets. The magnets are secured to the supporting member 2 by means of screw-bolts 15 which pass through slots in the support 2 to permit of vertical adjustment of the magnets, Such vertical adjustment to accurately center the armature 14 in the air gaps of the magnets is provided b the adjusting screws 16 and 17 which pass tlirough the posts 10 and 11.

The actuating coils 18 surround the armature 14 and are secured to a bracket 19 which is fastened to the support 2. The armature 14 is connected by a link 20 to the diaphragm 21. The diaphragm 21 is made of conical form to give it the desired rigidity without excessive weight. In the form illustrated, the base of the cone is secured to a ring 22 which may be of comparatively flexible material, suchas mica, and the ring 22 is clamped between a ring 23, which is secured to the support 2, and a clamping ring 24: by means of the screws 25. A narrow sound chamber with an outlet 26 is formed by means of the cover 27. The tubular extension 28 of the cover 27 provides a means for securing to the device a horn of any desired form. The protective casing 29 encloses the actuating mechanism of the device.

A diaphragm actuating element such as described may be made so rigid that any natural vibration frequency which it possesses will be above the frequencies of the sounds to be reproduced, and hence no distortion of the sound will be. produced by reason of this element. The conical portion of the diaphragm 21 will also move as a whole, substantially no relative movement between different portions being produced by the actuation of the diaphragm. Substantially all of the internal stresses produced in the diaphragm will be produced in the ring 22.

It will also be observed that the center of the diaphragm is located directly above the center of the actuating element, and that the connecting link 20 moves straight up and down, thus permitting the use of a rigid connection of the connecting link to both the diaphragm and the actuating element. By this construction none of the energy available is uselessly employed in bending the connecting link, and the connection is free from any lost motion such as isinherent in any link connection involving two or more members having relative movement with respect to one another.

The actuating element 12 may, if desired, be so constructed that a portion of the bend ing thereof will take place in the middle portion which is located in the air gaps of the magnets 3 and 4. Preferably, however, the armature 14 is made thick enough to reinforce the middle portion to such an extent that substantially all of the bending will occur in the end portions of the actuating element between the armature'14 and the supports. As a result of such construction the armature moves as a whole across the air gaps with substantially the same relative movement between all parts thereof and the poles of the-magnet and no relative movement between ditferent parts thereof, and the attraction between thearmature and the nearest magnet pole is substantially uniform throughout the entire area of the air gaps whenever the actuating element is deflected from its central position.

While I have shown and described the preferred embodiment of my invention, it will be apparent that my invention is by no means limited to the precise embodiment shown, but that many modifications therein may be made without departing from the scope of myinvention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. A sound reproducing device comprising a diaphragm actuating element consisting of a tubular member rigidly supported at its ends and flattened at its middle portion.

2. A sound reproducing device comprising a diaphragmactuating element consisting of a tubular member of non-magnetic material supported at its ends and flattened at its middle portion, and a member of magnetic material secured .to the middle portion thereof.

8. A sound reproducing device comprising a diaphragm actuating element consisting of a tubular member of non-magnetic material rigidly supported at its ends and flattened at its middle portion.

4. A sound reproducing device comprising a diaphragm actuating element consisting of a comparatively light elongated rigid member which is rigidly supported at its ends and is more flexible at its end portions than at its middle portion. i

5. In a sound reproducing device a diaphragm actuating element comprising a comparatively light elongated ri id member of non-magnetic material which 1s supported at its ends and is more flexible at its end portions than at its middle portion.

6. A sound reproducing device comprising a diaphragm actuating element consisting of a comparatively light elongated rigid member of non-magnetic material which is supported at its ends and a member of magnetic material secured to its middle portion, said element-being more flexible at its end portions than at its middle portion.

7. A sound reproducing device comprising a diaphragm actuating element consisting of an elongated member of non-magnetic material supported at its ends, a member of mag netic material secured to its middle portion, and a pair of magnets each of which has a pair of opposing poles separated by a short air gap, the middle portion of said element being supported in the air gaps of said magnets.

8: A sound reproducing device comprising a diaphragm actuating element consisting of an elongated member rigidly supported at its ends and a pair" of magnets each of which has a pair of opposing poles separated by a short air gap, themiddle portion of said element being supported'in the air gaps of said magnets, and an actuating coil surrounding the middle portion} of said element.

9. A sound reproducing device comprising a diaphragm actuating element consisting of an elongated member of non-magnetic material supported at its ends, a member of magnetic material secured to its middle pore tion, anda pair of magnets each of which has a pair of opposing poles separated by a short air gap, the middle portion of said actuating element being supported in the air gaps of said magnets, and an actuating coil surround ing the middle portion of said actuating element.

1O. A sound reproducing device comprising-a diaphragm actuating element consisting of a tubular member supported at its ends and flattened at its middle portion, and a pair of magnets each of which has a pair of opposing; poles separated by a short air gap, the flattened middle portion of said element being'supported in the air gap of said magnets.

' 11. A sound reproducing device comprising a diaphragm actuating element consisting of a tubular member of non-magnetic material supported at its ends and flattened at its middle portion, a member of magnetic material secured to its flattened middle portion, and a pair of magnets each of which has a pair of opposing poles separated by 'a short air gap, the flattened middle portion of said.

element being supported inthe air gaps of said magnets.

12.A sound reproducing device comprising a diaphragm actuating element consisting of a tubular member of non-magnetic material supported at its ends and flattened at its middle portion, a member of magnetic ma terial secured to its flattened middle portion,

and a pair of magnets each of which has a pair of opposing poles. separated by a short air gap, the flattened middle portion of said element being supported in the air gapsof said magnets, and an actuatingcoil surrounding the flattened middle portion of said element between said magnets.

13. A sound reproducing device comprising a diaphragm, a rigid diaphragm actuating element supported atits ends and having its middle portion located in a short air gap between opposing magnetic poles, and a rigid connection between the center of said element and the center of said diaphragm, the natural frequency of vibration of said element being greater than that of the sounds to be reproduced.

14. A sound reproducing device comprising a diaphragm, an elongated diaphragm actuating element supported at its ends and having its middle portion locatedv in an air gap between opposing magnetic poles which is short in comparison with the Width of said element, the center of said diaphragm being directly above the center of said actuating cle ment, and a rigid connection between the center of said diaphragm and the center of said actuating element.

flattened at its middle portion, a member of magnetic material secured to the middle portion thereof, and a rigid connection between said diaphragm and said. actuating element. 17 A sound reproducing device compris ing a diaphragm, a diaphragm actuating element consisting of a tubular member of nonmagnetic material supported at its ends and flattened. at its middle portion, and a rigid connection between said diaphragm and said actuating element.

18. Asound reproducing device comprising a diaphragm, a diaphragm actuating element consisting of a comparatively rigid member which is supported at its ends and is more flexible at its end portions than at its middle portidm, and a rigid connection between said diaphragm and said actuating element, the natural frequency of vibration of said element being greater than that of the sounds to be reproduced.

19. A sound reproducing device comprising a diaphragm, a magnet having a pair of opposing poles separated by a short air gap, a diaphragm actuating element consisting of a rigid elongated member supported at its ends and having its middle portion located in the air gap of said magnet, and a rigid connection between the center of said diaphragm and the center of said actuating element, the natural frequency of vibration ofsaid element being greater than that of the sounds to be reproduced.

20. A sound reproducing device compris of which has a pair of opposing poles sepa rated by a short air gap, the middle portion of said element being supported in the air gaps of said ma 'ne'ts, an actuating coil surrounding the middle portionof said element, and a rigid connection between the center of said diaphragm and the center of said v actuating element.

21. A sound reproducing device comprising a diaphragm, a diaphragm actuating ele ment consisting of an elongated member supported at its ends, a pa-irof magnets each of which has a pair of opposing poles separated by a short air gap, the middle portion of said element being supported in the air gaps of said magnets, an actuating coil surrounding the middle portion of said element, and a straight connectin link rigidly secured to the center of said ter of said actuating element.

22. A sound reproducing device comprising a diaphragm, a relatively rigid diaphragm actuating element supported atits ends, an actuating coil surrounding said element, and a rigid connection between the center of said element and the center of said diaphragm.

23. A sound reproducing device comprising a diaphragm, a relatively rigid diaphragm actuating element supported. at its ends, the center of said diaphragm being located directy above the center of said actuating element, an actuating coil surrounding said element, and a rigid connection between the center of said element and the center of said diaphragm.

24. A sound reproducing device comprising a diaphragm, a rigid diaphragm actuating element supported'at'its .ends, the center of said diaphragm being located directly above the center of said actuating element, an actuating coil surrounding said element, and a straight connecting link rigidly secured to the center of said diaphragm and to the center of said actuating element.

25. A sound reproducing device comprising a diaphragm actuating element consisting of a tubular member of non-magnetic ma terial supported at its ends and flattened and reinforced at its middle portion by magnetic material so that the end portions are more flexible than the middle portion.

26. A sound reproducing device comprising a diaphragm actuating element consistin of an elongated member supported at its en cls, said member being more flexible at its end portions than at its middle portion, and a pair of magnets each of which has a pair of opposing poles separated by a short air gap, the middle portion of said element being supported in the air gaps of said magnets,

and an actuating coil surrounding the middle portion of said element.

- 27. A sound reproducing device comprising a diaphragm actuating element consist son with the wi diaphragm and to the cening of a tubular member 'ofnon-magnetic material supported at its ends and flattened at its middle portion, a member of magnetic material secured to its flattened middle portion and reinforcing the middle portion to make the middle portion more rigid than the end portions, an'd'a pair of'magnets each of which has a pair' of opposing poles separated by a short air gap, the flattened middle portion of said element being supported in the air gaps of said magnets. 28. A sound reproducing device comprising a diaphragm, a magnet having a pair of opposing poles separated by an air gap, a diaphragm actuating element comprising an armature located in the air gapof said magnet, said air ap being short in comparidth of said armature, said armature being so constructed and arranged that when actuated all parts thereof in the air gap will have substantially the same relative movement with respect to the magnet poles, and a rigid connection between the ar-- mature and the diaphragm.

29. A sound reproducing device comprising a magnet having a pair of opposin poles separated by an air gap and a diap ragm actuating element comprising a member of magnetic material located in the air gap of said magnet, said air gap being short in com-- parison with the width of said member, said member being so constructed and supported that when actuated all parts thereofin the air gap will have substantially the same relativle movement with respect to the magnet p0 es.

30. A sound reproducing device comprising a conical diaphragm of light rigid material, a ring of more flexiblematerial secured to the outer edge of said diaphragm, supporting means for said ring of flexible material, an elongated vibratory member provided with a resilient bendable support and located in a pair of short air gaps between opposing magnetic poles, an actuating coil surrounding the middle portion of said member and a connecting rod between said member and the central portion of said diaphragm. v p

31. A sound reproducing device comprising a conical diaphragm of light rigid material, a ring of more flexible material secured to the outer edge of said diaphragm, supporting 'means for said ring offlexible material, an elongated vibratory member provided with a-resilient bendable support and located in a pair of short air gaps between opposing magnetic poles, means for vibrating said member, and a connecting rod between said member and the central portion of said diaphragm.

ing aconical'diaphragm of light rigid-mate 32. a sound reproducing device comprisporting means for said ring of flexible material, a vibrating member provided with a resilient'bendable support and of magnetic material located in a pair of short air gaps between opposing magnetic poles,an actuating coil surrounding the middle portion of said member and a connecting rod between said member and the central portion of said diaphragm.

m 33. A current responsive device comprising an actuating element consisting of an elongated member rigidly supported at its endsand a pair of magnets each of which has a pair of opposing poles separated by a short air gap, the middle portion of said element being supported in the air gaps of said magnets and an actuating coil surrounding the middle portion of said element.

34. A current responsive device comprising an actuating element consisting of a tubular member of non-magnetic material supported at its ends and flattened at its middle portion, a member of magnetic material secured to its flattened middle portion, and a pair of magnets each of which has a pairof opposing poles separated by a shortair gap, the flattened middle portion of said element being supported in the air gaps of said magnet.

In witness whereof, I have hereunto set my hand this 12th day of September, 1922.

CHARLES A. HOXIE. 

